1 Field of the Invention
The present invention generally relates to printers for printing a video image and, more particularly, is directed to a printer which is suitably applied to a multi-scan video printer for printing video input signals of different kinds.
2. Description of the Prior Art
A multi-scan video printer is proposed in the art, in which different kinds of input signals, for example, an NTSC video input signal and a video input signal from a personal computer are inputted to one printing apparatus and video images corresponding to these video input signals can be printed on a recording paper by a thermal print head or the like.
The multi-scan video printer is supplied with an input signal having scanning lines and horizontal scanning frequency considerably different from scanning lines, horizontal scanning frequency and aspect ratio or the like of a television video signal when video images of various living bodies for medical use are printed out.
When the scanning lines and horizontal scanning frequency of the video input signals supplied to the multi-scan video printer are changed as described above, various values of the following items must be manually determined in the conventional multi-scan video printer:
(1) Value of the printing area in the horizontal direction of a memory within the multi-scan video printer; PA1 (2) Value of the printing area in the vertical direction of the memory within the multi-scan video printer; PA1 (3) Number of sampling dots, i.e. sampling frequency; within one horizontal period; PA1 (4) Value of printing size in the horizontal direction to be printed (dimension of lateral direction of printing); and PA1 (5) Value of printing size in the vertical direction to be printed (dimension of longitudinal direction of printing).
The above-described values of various kinds cannot be inputted to the multi-scan video printer by those who have insufficient understanding of video signals inputted to the multi-scan video printer.
Incidentally, in the aforenoted multi-scan video printer, a storage capacity of a memory is determined so that a television signal of the system in which an input video signal has much more horizontal scanning lines can be stored therein.
The storage capacity of the memory in the multi-scan video printer is determined constant. For example, assuming that the storage capacity of the memory is determined to store therein data of 1024.times.1024 bits, then an input video signal of 1024 dots .times.500 lines is stored in the memory of such multi-scan video printer and the input video signal stored therein is read out. However, upon printing, only one sheet of video image of the input video signal can be printed. More specifically, from a memory storage capacity standpoint, if the input video signal of 1024 dots .times.500 lines is inputted to the memory of the above-described storage capacity, this multi-scan video printer could print two sheets of video image of such input video signal but can print only one sheet of video image, thus making the storage capacity of one picture amount useless.
Furthermore, if video signals inputted to the multi-scan video printer are different, then video images of different dimensions are printed out. The condition that video images are printed out in different sizes will be described with reference to FIGS. 1A-1C.
Let us consider a television picture 32 shown in FIG. 1A. In that case, let us assume that a horizontal scanning line number l in the vertical direction V is 525 and that its dot number in the horizontal scanning direction H is a dots, for example, 1500 dots. Also, let it be assumed that an effective dot number in the line direction of a thermal print head 20 is 1216 dots as shown in FIG. 1B and that the television picture 32 long in the width direction shown in FIG. 1A is stored in the memory under this condition. Further, let it be assumed that the printing is performed under the condition that the longitudinal direction (i.e. direction of a dots) of the television picture 32 is matched with the longitudinal direction of the printing paper 21 as shown in FIG. 1B and that, for example, the horizontal scanning line l in the vertical direction and the dot number of the thermal print head 20 in the horizontal scanning line direction are made corresponding to each other as 1 : 1. Then, l=525 lines correspond to l=525 dots so that the television picture 32 is generally printed as shown in FIG. 1B, thus the television picture 32 being printed out small because l is equal to 525 dots as compared with the effective dot number of the thermal print head 20 presented as h=1216 dots. The a dots in the printing paper moving direction are determined by the printing paper moving pitch and the printing is carried out under the condition that the pitch of one dot of a dots, i.e. 1/1500 dot is made corresponding to the aspect ratio of the television picture 32. If the number of horizontal scanning lines in the vertical direction of the input video signal inputted to the printer becomes different as described above, the television picture is printed out in different printing size.
Further, if a television picture long in the width direction similarly to the television picture 32 shown in FIG. 1A is printed on the printing paper 21 as shown in FIG. 1C, the dot number a in the horizontal direction is not always made constant due to analog-to-digital (A/D) conversion in the printer and the restriction of upper limit of the sampling frequency of the memory or the like. As a result, there is the substantial disadvantage that the printing size is changed in accordance with a plurality of different input video signals.
In the aforenoted multi-scan video printer in which the video image is always printed out in the same size of longitudinal and lateral directions, there is the problem that the video image cannot be printed out in size corresponding to the aspect ratio of television pictures of different video input signals.
Furthermore, in a video printer in which the printing size is enlarged by the double printing, it must be determined by the manual operation whether or not the video image is printed out in an enlarged scale. Therefore, if the user does not fully understand the features of a plurality of different video input signals inputted to the multi-scan video printer, the printing size cannot be determined precisely, thus making it impossible to operate an enlarging button of the multi-scan video printer.